The invention relates generally to a processing arrangement and method, especially for developing photosensitive articles.
More particularly, the invention relates to an arrangement for and a method of regenerating a processing bath.
It is known to add a regenerating solution to a processing bath in a photographic developing apparatus in order to maintain the consistency or concentration of the bath constant. The regenerating solution compensates for the changes which occur in the processing bath due to use or aging. Such an apparatus generally has sensing devices which sense the surface areas of the photosensitive articles advanced into the bath. The quantity of regenerating solution required is automatically calculated from the surface areas and this quantity is added to the bath via a regulating device.
A variety of arrangements for controlling the addition of the regenerating solution to the processing bath exists. These arrangements are connected to the sensing devices which measure the surface areas of the photosensitive articles and control the addition of the regenerating solution to the bath in dependence upon the measurements of the surface areas. The introduction of the regenerating solution into the bath is usually performed by a pump.
In one conventional arrangement, the required quantity of the regenerating solution is added to the bath by operating the pump for a predetermined number of strokes. It is assumed that a fixed quantity of the regenerating solution is discharged into the bath for each stroke of the pump.
It is also known to add the regenerating solution to the bath via a solenoid valve. On the assumption that a fixed quantity of the regenerating solution will flow through the valve per unit of time, the required quantity of the regenerating solution is added to the bath by keeping the valve open for an appropriate, predetermined time interval.
It has been found that impurities can deposit and thus reduce the flow cross section for the regenerating solution. When this occurs, the quantity of regenerating solution delivered per stroke of the pump and, likewise, the quantity of regenerating solution flowing through the valve per unit of time will no longer be constant. Accordingly, operation of the pump for a predetermined number of strokes or holding of the valve in an open position for a predetermined time interval will not result in delivery of the required quantity of regenerating solution to the processing bath. The same holds true if leaks are present.